Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed Oct. 16, 2007). Vita. Includes bibliographical references.

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Nucleotide pools were extracted and quantified from Pyr^+ and Pyr^- strains of P. aerucjinosa. Strains were grown in succinate minimal medium with and without pyrimidines, and nucleotides were extracted using trichloracetic acid (TCA; 6% w/v). The pyrimidine requirement was satisfied by uracil, uridine, cytosine or cytidine. Pyr^- mutants were starved for pyrimidines for two hours before nucleotide levels were measured. This starvation depleted the nucleotide pools which were restored to wild type levels by the addition of pyrimidines to the medium. When the pyrimidine analogue, 6-azauracil, known to inhibit OMP decarboxylase, was added to cultures of the wild type strain, the uridine and cytidine nucleotides were depleted to near zero. Thus, the nucleotide pool levels of Pseudomonas strains can be manipulated.

Some compounds, analogous to those found in naturally occurring systems, are found to possess chemotherapeutic activity. Some, in the form of their nucleoside or nucleotide derivatives, are valuable antimetabolites in that they may block normal RNA or DNA polymerisation, or may be incorporated into nucleic acids to form fraudulent, but not necessarily defective, polymers. Modification of natural ring systems, with a view to promoting chemotherapeutic activity is therefore of considerable interest; variation in the position and nature of the modification or ring substituent having a marked effect on chemotherapeutic activity. It is the purpose of this thesis to suggest methods for the facile synthesis of various uracils, pyrazoles and pyrazolo [3,4-d] - pyrimidines with alkyl, aryl and glycosyl substituents such that the nature of the ring substituents is easily varied. To this end a number of ethoxymethylene reagents were prepared which, by reaction with primary amines and hydrazines, would give acyclic intermediates capable of easy cyclisation into the uracil, pyrazole and pyrazolo [3,4-d] pyrimidine ring systems. Variation in the nature of specific substituents being determined by the choice of amine or hydrazine, other substituents being varied by modification of the original reagent. / S.R.G.

Call number: LD2668 .T4 1965 C559 / Master of Science

Chapter 1 of thesis is a literature review of adenosine research. The central importance of the contributions of both classical pharmacology and, more recently, molecular biology to adenosine research is demonstrated. These disciplines have enabled the classification and characterisation of adenosine receptors and as well an understanding of the physiological significance of endogenous adenosine. The significant benefits of developing therapeutics for regulation of the diverse physiological functions of adenosine, by regulation of adenosine receptors, is outlined. For this therapeutic potential to be realised both high affinity and subtype selective adenosine agonists and antagonists are required. The structure-activity relationships for agonists and xanthine antagonists are discussed. The assimilation of these structure-activity relationships have guided the development of ligand based models of the adenosine receptor pharmacophore. The 'flipped', 'N6-C8' and 'three binding domain' models were described. These models aim to direct the future design of high affinity and selective ligands for adenosine receptors. The development of receptor based models by modelling of the receptor-ligand complex is also presented. The main body of this thesis presents a study of the structure-activity relationships for pyrazolo(3,4-d) pyrimidines binding to adenosine Ai and A2a receptors. Prior to this study few non-xanthine adenosine antagonists had been well defined or optimised in terms of structure-activity relationships. However, the value of such ligands is immense, facilitating further definition of structural requirements for high affinity and selective adenosine receptor binding. These ligands should complement existing agonists and xanthine antagonists in developing an understanding of adenosine receptor binding. The experimental approach to development of the lead compound of this study, a-(6-(l'-carbamoylethylthio)- l-phenylpyrazolo(3,4-d)pyrimidin-4-ylthio)propanamide (5), is outlined in Chapter 2 of this thesis. 5 is substituted at C-4, C-6 and N-i of the pyrazolo(3,4-d)pyrimidine heterocycle. The experimental approach to optiniising 5 was approached in a rational manner, requiring an iterative approach i.e. design of generation I target compounds --synthesis -- biological evaluation -- structure-activity relationships -- design of generation II target compounds, etc. Chapters 3, 4 and 5 of this thesis describe this experimental approach as it relates to optimising the lead compound, 5, for adenosine receptor affinity and subtype selectivity. The importance of receptor interactions with multiple ligand domains, to achieve both potency and selectivity, was recognised so that optimisation of the C-4, C-6 and N-i substituents of the lead compound was targeted and achieved. Previous structure-activity studies with agonists and xanthine antagonists have concentrated on modifying a single ligand domain. Chapter 3 presents twelve generation I target compounds to examine C-4 and C-6 substituent structure-activity relationships. Chapter 4 presents twelve generation II target compounds to further examine C-4 and C-6 substituent structure-activity relationships. Chapter 5 presents sixteen generation ifi target compounds to examine N-I substituent structure-activity relationships. A major outcome from the research presented in these chapters was the development of highly potent and highly selective ligands for the adenosine A1 receptor subtype. a(4-Methylamino- I -phenylpyrazolo(3,4-d)pyrimidin-6-ylthio)hexanamide (29) was the most potent ligand at the Ai receptor identified in this study, and is one of the most potent Ai selective antagonists ever reported. 29 has an A1 K1 value of 0.745±0.045 nM and is 332-fold selective for the A1 receptor over the A2a receptor. a-(1-Phenyl-4-propylthiopyrazolo(3,4-d)pyrimidin-6-ylthio)butanainide (27) was the most selective ligand of this study. It is four orders of magnitude selective for the A1 receptor (up to 16900-fold), and one of the most selective antagonists ever reported. This high selectivity has been achieved with the maintenance of good A1 affinity (A1 K1 = 29.5±6.6 nM). These results prove the value of modifying multiple substituents of adenosine receptor ligands, generating ligands which bind with high potency and selectivity to adenosine Al receptors compared to adenosine A2a receptors.

Thesis (Ph.D.) - University of St Andrews, January 2007. / Restricted until 30th January 2010.

Call number: LD2668 .T4 1958 M88

A facile method for the synthesis of highly enriched ¹⁸O labeled pyrimidine ribonucleosides is described. The ribonucleoside may be labelled specifically in the base, the sugar, or both moieties with one or two oxygen-18 atoms. The isotopic purity of the products as well as the location of the oxygen-18 labels have been unambiguously determined by mass spectrometry. Stable isotope labeled analogs have been employed to determine the composition of several clinically significant nucleoside dialdehydes by mass spectrometry. Formation of the trimethylsilyl derivatives permits the gas chromatographic separation of the major components present in the equilibrium mixture. In addition to the expected hemiacetals and hydrates, a substantial amount of the dialdehydes exist in polymeric form. Fast atom bombardment mass spectrometry enabled observation of dimeric and trimeric species from the polymeric material present in the mixture.